The invention relates to oxy-acetylene and the like gas torches, and in particular to those which have application to the sprayed deposition of metal or other powdered material to form a coating on a substrate. Such torches are exemplified by constructions disclosed in Huhne et al. U.S. Pat. No. 3,986,668.
A torch of the character indicated must be able to apply intense heat to the powder material to be sprayed, and the problem of high-heat delivery for a given size torch increases as higher-temperature materials become available or are specified for incorporation in the powder formulation. Higher heat delivery means greater flows of oxygen and of fuel gas, and thus larger gas-flow passages, with increasing susceptibility to "flash-back", involving shock-wave transmission through the mixed-gas distribution system; and shock-wave incidence at the mixing locale is sufficient to extinguish the torch, thus frustrating the otherwise uniform coating or other function of the torch, and sometimes requiring rejection or costly reworking of the incompletely coated substrate article.